Phenol is manufactured via air oxidation of cumene to cumene hydroperoxide (CHP), followed by acid-catalyzed cleavage of the latter to phenol and acetone, and known as CHP decomposition. CHP decomposition is a very exothermic reaction which is normally carried out on a commercial scale in continuous stirred or back-mixed reactors. In such reactors only a small fraction of CHP is unreacted at any given time and the reaction medium consists essentially of the products of decomposition of CHP, i.e., phenol and acetone, plus any solvent (e.g., cumene) and other materials added with CHP to the reactor. During cumene oxidation small amounts of dimethyl phenyl carbinol (DMPC) and acetophenone are also formed. In the presence of acid catalyst, DMPC dehydrates to alphamethylstyrene (AMS), a useful by-product.
The traditional design of phenol fractionation flow scheme includes two columns that are used to separate the acetone, cumene, and AMS in the fractionation feed from the phenol. Acetone and a portion of the cumene and water are first distilled to the overheads of the crude acetone column (first column), which operates at slightly above the atmospheric pressure. Acids in the overhead streams would lead to fouling in the subsequent system. The bottoms, containing the remainder of the cumene and water and the bulk of formic acid and acetic acid, along with essentially all of the AMS, phenol and higher-boiling by-products are routed to the cumene-AMS column (second column), which operates at fairly deep vacuum. However, there is need to separate the phenol contaminants and impurities in a separate system downstream the phenol fractionation column with two columns.
The use of such multiple systems for phenol fractionation results in increased capital equipment costs and operating costs. The conventional design of single distillation column known in the prior art do not yield high recoveries of acetone and phenol. There is a need for a new process and apparatus to efficiently operate the phenol unit with significant reduction in the capital and operating costs. Also, there is a need for an improved and more economical process and simplified apparatus design for the phenol fractionation that can improve the yield of phenol and acetone.